The complex origins of the North American Ephemeroptera fauna extended from the Lower Permian to the Recent. This paper discusses origins of North American genera of the cosmopolitan family Leptophlebiidae with a few examples from other mayfly families. The two extant subfamilies, Leptophlebiinae and Atalophlebiinae, probably evolved at least by the mid-Cretaceous, or about 100 million years before present. The primitive Leptophlebiinae are distributed throughout most of the Northern Hemisphere and the ancestors of the Leptophlebia–Paraleptophlebia complex within this subfamily dispersed widely by the North Atlantic route as early as the mid-Cretaceous and later probably by northern trans-Pacific dispersals through Beringia. The ancestors of Habrophlebia dispersed through the North Atlantic route at an early time, but the vicariant distribution of Habrophlebiodes in several areas of the Oriental Region and eastern North America correlates with the Arcto-Tertiary forest that covered most of the Northern Hemisphere including Beringia from the Early Tertiary into the Pleistocene. Within the nearly cosmopolitan Atalophlebiinae, Traverella is austral in origin and probably dispersed north through the Mexican Transition Zone during the mid-Tertiary as an ancient dispersal and then dispersed to its northern and eastern limits following the last Pleistocene deglaciation by way of the Missouri River tributaries. Thraulodes and Farrodes are both austral in origin and probably dispersed north through the Mexican Transition Zone during the Early Pleistocene as a relatively recent dispersal. The origins of Choroterpes sensu stricto and Neochoroterpes in North America are unknown. The mayfly fauna of the West Indies is Neotropical in origins, and no affinities between the West Indies and North America through Florida have ever been confirmed.

Mecoptera of the Nearctic Region are, in general, more like those of the eastern Palaearctic than of any other faunal region. But the fossil record shows that our major extant genera have been in the northern continents since Early Cenozoic. Panorpidae and Panorpodidae probably entered North America by way of Beringia in the Eocene or Oligocene. Nearctic Bittacidae probably came from the Neotropical Region, but a few exhibit peculiar affinities with some eastern Asiatic species, suggesting migration out of the Nearctic into the Palaearctic. Boreidae appear to have been of North American origin but are now Holarctic; they are unknown as fossils. The Meropeidae were probably widespread in mid–Mesozoic but now are found only in eastern North America and western Australia.

The present distributions of stonefly genera in North America, their occurrence as endemics, or as shared with the Far East, Europe and South America, are considered in conjunction with geological history. It is concluded that the Plecoptera of North America have four sources of origin.There was an ancient eastern fauna shared with Europe before the formation of the North Atlantic Ocean. A second group moved in from the west during the formation of the western mountains. After formation of the isthmus one genus moved northward from South America. After the Pleistocene period several species migrated from the Bering Strait region, possibly from an Alaskan refugium. Some of these have clearly moved eastward, but a few may have moved westward.

The supercontinent of Pangaea, which once included most lands, fragmented during the Mesozoic. By the Late Cretaceous there were two northern land masses that were strikingly different from those of present day: Asiamerica consisting of present western North America and Asia; and Euramerica comprising Europe and eastern North America. Mild climates facilitated the spread of terrestrial organisms within each of these land masses, but epicontinental seas hindered movements between Europe and Asia and between eastern and western North America.The insects of Euramerica presumably once formed a fauna extending from eastern North America to Europe that differed from the fauna of Asiamerica. The opening of the North Atlantic separated insects in Europe from those in eastern North America. This produced vicarious patterns, with some insects of eastern North America now being more closely related phylogenetically to those of Europe than to those of western North America. Most groups of insects have not been examined for such trans-Atlantic vicariances, but studies reviewed in this paper suggest such relationships for some groups of Collembola, Hemiptera, Homoptera, Coleoptera, Diptera, and Hymenoptera.The last suitable land connections between Europe and eastern North America were severed approximately 20–35 million years ago. The insects separated by this severance evolved at different rates. Some groups split in this way have apparently undergone little evolution and have the same species on both sides of the North Atlantic, but other vicarious groups have differentiated into taxa that are now distinct at specific and supra-specific levels.The opening of the North Atlantic probably split both tropical- and temperate-adapted insects in Euramerica. However, without fossil data it is difficult to identify the biogeographical patterns resulting from such splitting of the tropical-adapted groups. Most presently recognized European and eastern North American vicarious patterns of insects were probably caused by division of Euramerica rather than dispersal across Beringia.

The paper discusses the nature and origins of the present-day insect faunas of Greenland, Iceland, and the Faeroes in relation to those of North America and Europe. The markedly warm-adapted faunas of the Early Tertiary were modified or eliminated as the climate cooled from the Oligocene onward to the Pleistocene glaciations. The Wisconsinan glaciation peaked about 20 000 years ago, and then gave way rapidly to the arctic and cool temperate climates of the present, and the North Atlantic islands thus became habitable again but separated by wide expanses of northern seas. At most only a few strongly arctic-adapted species could have persisted through the Pleistocene and no land bridges from the continents have existed since the Early Miocene, 20 million years ago.Southern Greenland, Iceland, and the Faeroes have been colonized across sea passages from the adjacent continents, mainly by air but partly by sea, during the postglacial period (ca. 10 000 years). The faunas are all young, with no endemic species among about 2000 in all; the faunas are not arctic but distinctly subarctic, mainly of the High and Low Boreal life zones, and derived from these life zones of North America or Europe. The naturally established faunas are small or very small, less than 14% of the corresponding continental faunas, and are obviously disharmonic, with some groups absent across the North Atlantic, e.g. Culicidae, Tabanidae, Tachinidae, Papilionoidea, aculeate Hymenoptera (except Bombus sp.). This indicates a severe "sweepstakes" route. The lack of Tachinidae is noteworthy because their hosts are plentiful, and indicates dispersal by air, with adult Tachinidae, unlike adult Lepidoptera, unable to make the journey; dispersal by a land bridge would offer parasites and hosts an equal opportunity. Aerial transport is indicated also by the high proportion of migrant species (of Lepidoptera) in the island faunas, and the arrival in Surtsey (a new volcanic island) of almost 25% of the Icelandic fauna in 12 years. The Surtsey observations suggest that the Icelandic fauna is preadapted to aerial dispersal, by selection during its journey from Europe.The fauna of southern Greenland is derived partly from boreal America and partly from boreal Europe. The North American moiety becomes vestigial in Iceland and the Faeroes and does not reach Europe. Iceland and the Faeroes have been populated from northwestern Europe, especially Britain and Scandinavia. A few species extend to southern Greenland and thence, or even directly, reach North America, and have thus completed a post-glacial traverse of the North Atlantic.The fauna of North Greenland differs fundamentally from all the above. It is a high arctic fauna, nearly identical with the high arctic fauna in Canada, and thus complete, not disharmonie, though very small by virtue of its high arctic nature. It has encountered no "sweepstakes" dispersal. North Greenland is separated from High Arctic Canada only by a narrow channel which permits winter dispersal by wind across unbroken sea ice. Biologically, North Greenland is part of the North American High Arctic, and although certain species (e.g. mosquitoes and butterflies) may extend somewhat into southern Greenland, it has not contributed to the basic faunas of the North Atlantic islands.Among other problems, the extreme variability in wing pattern of many Lepidoptera in Iceland, the Faeroes, and Shetland is also commented on.

Fossils from sites of Late Quaternary age in North America provide tangible evidence of temporal changes in the character of the northern beetle fauna. Based on a synthesis of the fossil data with analyses of the present distributions for northern species, a rudimentary model is proposed to explain the recent history of the fauna of the arctic and the boreal forest.An open-ground beetle fauna of arctic–subarctic affinities had become established along the southern margin of the Laurentide ice sheet in the midcontinent by 20 500 years before present (yr B.P.). Climatic warming decimated this fauna throughout lowland areas at some time between 16 700 and 15 300 yr B.P.; small populations of some arctic–subarctic species, however, survived within either alpine habitats of the Cordillera and Appalachians or specialized environments associated with stagnant ice.Populations of the same arctic–subarctic beetle species existed within the ice-free Alaska–Yukon refugium throughout the late Wisconsinan. During the Holocene, this region served as the principal centre-of-origin for the dispersal of the arctic–subarctic beetle fauna.The beetle fauna of the boreal forest was also displaced southward by Late Wisconsinan glaciation. By 15 300 yr B.P., however, this fauna had largely replaced the arctic–subarctic beetle fauna along the ice margin of the midcontinent. Evidence provided by fossils from a series of sites demonstrates that beetle species of the boreal forest dispersed northward into Canada as the ice front receded.

The 245 species of Noctuidae known from Beringia, i.e. northwestern North America and northeastern Asia, are arranged in six groups based on their habitat preferences. These groups are analysed in terms of their distribution, endemism within Beringia, and zoogeographic affinities. The fauna associated with taiga, boreomontane forests and southern steppe (prairie) habitats shows only limited evidence of continuous occurrence in Beringia, and limited exchange during the Pleistocene between the Nearctic and Palaearctic. We have concluded therefore that this fauna has entered the Beringian area in Recent times following deglaciation of western and central Canada. In wet and dry tundra habitats, in contrast, there is abundant evidence of trans-Beringian faunal exchange. A high degree of endemism in dry tundra habitats within Beringia today is evidence of long-term stability of this habitat. These patterns, as well as evidence from a limited fossil sample of mid-Wisconsinan age, allow us to speculate on Beringian habitats during Wisconsinan times. We further conclude that the eastern Palaearctic and Beringia was the source area for the fauna that repopulated the Canadian Arctic after deglaciation. By contrast, non-Beringian refugia of the Nearctic have contributed little to the fauna of the Arctic.

The insect fauna of the Pacific Northwest Coast is diverse and rich in endemic forms. Nine different elements are recognized in the fauna, including (1) restricted coastal, (2) coast-centred, (3) Great Basin, (4) Rocky Mountain, (5) trans-American, (6) Holarctic, (7) trans-Beringian, (8) Alaskan, and (9) introduced elements. Elements (6), (7), and (8) are generally restricted to the northwestern portion of the coast; and representation of Rocky Mountain elements (4) increases in three major steps from south to north along the coast—at the Puget Lowland/Fraser River valley, the Prince Rupert area, and the Kenai Peninsula, respectively. Patterns of vicariance among sister taxa in the carabid beetle genus Nebria demonstrate relationships which, together with analyses of other faunal elements, show that the fauna of glaciated portions of the Coastal region has greatest affinity with faunas of southern coastal areas, less affinity with those of southern interior areas, and least affinity with faunas of northern areas. Areas of local endemism within the region include the Aleutian Archipelago, the southeastern Alaskan Panhandle, the Queen Charlotte Archipelago, the Olympic Peninsula/Vancouver Island, the northern Cascade Range, the Klamath Mountains system, and the Sierra Nevada. The extant coastal insect fauna has evolved from a widespread northern Tertiary fauna, elements of which were isolated in several separate refugia during Pleistocene glaciations. The northern two-thirds of the region has been recolonized in postglacial time from both coastal and interior refugia south of the Cordilleran and Laurentide ice sheets. Local endemism in the region reflects survival and differentiation of a few forms in small coastal refugia; but survivors from these refugia, as well as those from the Yukon/Beringian refugium, have generally been unable to extend their ranges to other parts of the Coastal region following deglaciation.

Assemblages of carabid beetles occurring in anthropogenic habitats in western Canada include native and introduced species. In this study, about 70% of the native species encountered in anthropogenic habitats have their main centres of abundance in native grassland. Twenty species known from British Columbia are of recent European origin. These species were probably introduced in ballast carried by commercial sailing vessels or in shipments of nursery stock. The species that have successfully colonized western Canada cannot be distinguished from a random sample of the estimated source fauna with respect to either taxonomic distribution or body size. However, all introduced species are characteristic of disturbed and/or anthropogenic habitats in Great Britain and are strictly synanthropic in British Columbia. Where they occurred, introduced species were usually numerically dominant members of anthropogenic assemblages. Both flight and human-assisted transport must be invoked to explain the patterns of range expansion observed for introduced species. Although the presence of introduced species was correlated with reduced diversity of native species, the carabid fauna of western Canada has been generally enriched because only one native species is strictly synanthropic.